IDENTIFICATION OF THE MANY-LINE VISIBLE EMISSION FROM THE CHEMILUMINESCENT REACTION OF $Ba(g) + N_{2}O$ AT $\bar{<} 10$ mTORR

Abstract

The identity of the electronic transitions giving rise to the low-pressure ($0.1 \sim 10$ mtorr) ``many-line spectrum^{\prime\prime} produced by the reaction $Ba(g) + N_{2}O\rightarrow BaO^{*} + N_{2}$ has been established by direct spectroscopic observations. Experiments that provided strong evidence regarding the emitters of this complex, headless spectrum consisted of spectrally resolving the $^BaO^{*}$ (electronically excited) visible chemiluminescence (4100-5500 {\AA}) at pressures of 5-10 mtorr as the diffusion flame stoichiometry was changed from metal-rich to oxidant-rich. Under oxiant-rich conditions, excess $N_{2} O$ partially rotationally relaxes the molecular emission to reveal that the nascent excited state products of this reaction are both $A^{\prime}{^{1} \Pi}^{+}$ and $A^{1} \Sigma^{+} BaO^{*}$. Identification of specific $A^{\prime} -X^{1}\Sigma^{+}$ and $A -X^{1}\Sigma^{+}$ vibrational transitions and analysis of their distribution have led us to conclude that the many-line spectrum is primarily the result of direct bimolecular reaction of Ba(g) with $N_{2} O$ to produce $^{B}aO^{*}$ with enormous rotational excitation. Results and conclusions about the other primary reaction product, the non-radiating precursor state, will also be discussed.